ICP vs home testing discrepancies

[bacheller3000]

7 months in to my reef tank, and I finally sent off water for an ICP test. I tested the water the day I took the sample with both Salifert and Hanna checkers. That day, Hanna checker had my Nitrates at 14.5. The Salifert test showed about the same. (The green color was somewhere between 10 & 20) I got the ICP results and it showed zero nitrates. So, I tested again the day I received the ICP results with just about the same values.(15ish) My question is, has anyone else experienced this? Is there an at home nitrate tester that you have found to be more accurate?
I’ve ordered another ICP test kit, as there were other discrepancies between results. I don’t want to take too many corrective actions too quickly. Salinity result from ICP was 30 ppm, when my 3 refractometers all read 35. I ordered the TM high precision hydrometer, and it was spot on with the ICP test results. I’ve slowly started bringing the salinity up to 35.

 

[Jay Hemdal]

7 months in to my reef tank, and I finally sent off water for an ICP test. I tested the water the day I took the sample with both Salifert and Hanna checkers. That day, Hanna checker had my Nitrates at 14.5. The Salifert test showed about the same. (The green color was somewhere between 10 & 20) I got the ICP results and it showed zero nitrates. So, I tested again the day I received the ICP results with just about the same values.(15ish) My question is, has anyone else experienced this? Is there an at home nitrate tester that you have found to be more accurate?
I’ve ordered another ICP test kit, as there were other discrepancies between results. I don’t want to take too many corrective actions too quickly. Salinity result from ICP was 30 ppm, when my 3 refractometers all read 35. I ordered the TM high precision hydrometer, and it was spot on with the ICP test results. I’ve slowly started bringing the salinity up to 35.

Your ICP results give nitrates? My test results only give elements, not compounds. They must be doing some other adjunct testing at the same time as they run your ICP.

 

[Randy Holmes-Farley]

The nitrate comes from other tests they do.

What company icp?

 

[bacheller3000]

The nitrate comes from other tests they do.

What company icp?

I used the MS test from the reef moonshiners site

 

[bacheller3000]

7 months in to my reef tank, and I finally sent off water for an ICP test. I tested the water the day I took the sample with both Salifert and Hanna checkers. That day, Hanna checker had my Nitrates at 14.5. The Salifert test showed about the same. (The green color was somewhere between 10 & 20) I got the ICP results and it showed zero nitrates. So, I tested again the day I received the ICP results with just about the same values.(15ish) My question is, has anyone else experienced this? Is there an at home nitrate tester that you have found to be more accurate?
I’ve ordered another ICP test kit, as there were other discrepancies between results. I don’t want to take too many corrective actions too quickly. Salinity result from ICP was 30 ppm, when my 3 refractometers all read 35. I ordered the TM high precision hydrometer, and it was spot on with the ICP test results. I’ve slowly started bringing the salinity up to 35.

Your ICP results give nitrates? My test results only give elements, not compounds. They must be doing some other adjunct testing at the same time as they run your ICP.

It was the MS-ICP test from the reef moonshiners website

 

[Dan_P]

It was the MS-ICP test from the reef moonshiners website

Sounds like Oceamo did the test which included a nitrate test with a different method. One way that Oceamo might detect zero nitrate while you detected nitrate is the presence of nitrite in the water sample.

 

[Randy Holmes-Farley]

Was it Oceamo? I’d trust their nitrate test. They use a method not interfered by nitrite (ion chromatography).

 

[bacheller3000]

Was it Oceamo? I’d trust their nitrate test. They use a method not interfered by nitrite (ion chromatography).

Yes, it was Oceamo

 

[billyocean]

Was there a feeding in close proximity to thr home test being done or are you still testing the same n03 range currently? Ive found oceamo to be pretty close to my hannas. Could just be a one off

 

[bacheller3000]

Was there a feeding in close proximity to thr home test being done or are you still testing the same n03 range currently? Ive found oceamo to be pretty close to my hannas. Could just be a one off

No, testing and samples were taken before the fish were fed that day. Main reason I immediately ordered another ICP test was because I find it VERY hard to believe my tank is running at zero nitrates.

 

[KStatefan]

All of my nitrate test compared Oceamo and Hanna have been close to the same value.
This year
27.2/30.97
40.8/39.06
14.4/14.39
10.1/9.14

 

[rtparty]

Your Salifert nitrate test is green? Not pink?

 

[bacheller3000]

Your Salifert nitrate test is green? Not pink?

By bad, yes it’s pink. Landing somewhere between the 10 and 25

 

[rtparty]

By bad, yes it’s pink. Landing somewhere between the 10 and 25

I wanted to double check just in case tests got mixed up or something

 

[disaster999]

ATI ICP test tests for nitrate and phosphates too. That test is inline with Salifert's nitrate and Hanna Checker's phosphate tests I did at home.

 

[rishma]

I had my last ICP come back 0/0 on nutrients and I know it wasn’t true. I suspect sample degradation but never figured it out for sure.

 

[Randy Holmes-Farley]

@Christoph

Any thoughts on nitrate changes between collection and testing?

 

[Christoph]

@Christoph

Any thoughts on nitrate changes between collection and testing?

We have not seen significant nitrate changes in filtered samples, even when stored for a long time. Home nitrate kits are very sensitive to interferences, and also the chemicals used are often quite delicate, so that nitrate testkits have the tendency to "go bad".

Getting the analysis number in question here would be helpful (please PM me), and i can check the raw data.

all the best, Christoph

 

[Randy Holmes-Farley]

Thank you, Christoph. :)

 

[JonasRoman]

It can be consumed in the sample after a few days. Its the same for phosphate. I have tested that many times. Especially if the water is not carbon limited. In my water it's consumed totally after 12 hours. Both po4 and no3. I also sent to a pro lab in medical field, to confirm. It was consumed. When I do an inorganic solution, not consumed.
The go around for that is to measure only P with ICP and then calculate phosphate. That is more reliable according to my opinion, even if that can give some false high po4 levels as you include potential organics. For no3 there is no go around

So for me, the distant lab is never to measure phosphate, nitrate, I think you shall do that yourself, and you use the ICP methods to measure things that cant change, thus atoms.